Consider a system with three fire pumps in parallel, where each pump can provide 100% of the required firewater. The two pumps are made by the same manufacturer, of the same model and are maintained in the same way. They are both located in the same room. Identify examples of intrinsic and extrinsic dependencies between the two pumps. From the three fire pumps in Problem 13.1, there are identical steel pipes supplying water to the users. The pipes are exposed to vibration causing fatigue, but the cracks do not develop exactly in the same way, such that all pipes fail within a few months of each other. Discuss whether this is a CCF or not. The three fire pumps in Problem 13.1 have failure rates of 1 × 10−⁵ h−¹. What is the probability that two pumps have failed after three months if we assume that there are no common-cause failures?